Conservation problems in the Neusiedler See–Seewinkel National ...

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332 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997 Fig. 1: Map of the Seewinkel region, Eastern Austria, comprising the salt pan area. Spider symbols indicate sites where Lycosa singoriensis occurs. & Zulka, 1994). Similarly, the area of extensively used pastures decreased from 3800 ha in 1855/58 to 815 ha, while reed areas increased from 1009 ha to 3016 ha, fragmenting once continuous open grassland. These tendencies have their common cause in the change from extensive land use to industrial agriculture and viniculture in the region, accompanied by irrigation, lowering of the ground water table (Krachler, 1993), drainage of salt pans, soil amelioration (Ghobadian, 1966), high fertilizer and pesticide application, habitat eutrophication, cessation of grazing, and spread of reed vegetation (Löffler, 1982). Extrapolating these trends and considering “eradication thresholds” (Nee, 1994), a complete loss of many typical halophilic organisms can be predicted for the near future in the region. To acknowledge the biodiversity importance of the region and to obtain a more effective conservation instrument, the Neusiedler See–Seewinkel National Park was established in 1994. Since the peripheral parts and buffer zones are mainly cultivated countryside, and many of the typical habitat types are the result of moderate human impact (Herzig, 1991), a consensus exists that appropriate management measures are of utmost importance to reverse detrimental trends. A grazing programme (Rauer & Kohler, 1990), however, revealed that much basic information for a successful implementation is still lacking, and that more accompanying monitoring programmes are urgently needed. Owing to their species richness and ecological specificity, spiders are appropriate indicators of habitat quality. We feel that data are necessary from four levels of complexity: (1) occurrence and distribution of species in the region; (2) assemblages of the major vegetation types; (3) habitat requirements of single species, in particular with regard to vegetation height. In this paper, we give an overview on efforts regarding these points. A fourth level, addressing the effects of spatio-temporal variation, disturbance frequency, patch dynamics, and habitat fragmentation, is largely a programme for the future. Species inventory The Seewinkel has been attracting zoologists for a long time (Löffler, 1982, and references therein). However, the first comprehensive spider inventory of the region was provided only in the fifties (Nemenz, 1958). A species accumulation curve (Gaston, 1996) can be used to assess the degree of completeness achieved by the studies performed in the region since then (cf. Thaler, 1980). With increasing sampling effort, the growth of the cumulative species number should be expected to dwindle, though a strict asymptotic behaviour cannot be expected, owing to the turnover in the species pool by immigration and extinction. The curve displayed in Figure 2 looks rather like the lower branch of a sigmoidal function than like an asymptote, and, compared to other Central European species inventories (e.g. Platen et al., 1995), the total of 213 species reached so far seems much too low for a nearly complete list. Thus, even basic faunistic information is inadequate in the region. The spider fauna of many Seewinkel regions (e.g. Hanság, Seedamm) is still completely unexplored. Even for spider species which are traditionally recognized as highly typical elements of the
Zulka and Milasowszky: Conservation problems in Seewinkel, Austria 333 region, the state of knowledge is often unsatisfactory. Lycosa singoriensis (Laxmann) is the largest Central European spider. Distributed across the Eurasian steppe belt, it reaches its westernmost outpost in Eastern Austria (Kratochvíl, 1932). Although it has been mentioned in many entomological publications on the region (e.g. Machura, 1935; Mazek-Fialla, 1936; see also references in Milasowszky & Zulka, 1996), its local distribution and habitat requirements have never been assessed in detail. When mapping its local occurrence (Milasowszky & Zulka, 1996), we found 8 sites housing 14 colonies that can be grouped into 3 isolated areas (Fig. 1). While prospects for the colonies around Illmitz seem to be good, colonies on the eastern salt pans are small, isolated and doomed to extinction. Numbers caught U G Dominant species (>100 individuals) Pardosa agrestis (Westring) 4 1482 Ozyptila simplex (O. P.-Cambridge) 134 561 Pardosa prativaga (L. Koch) 587 71 Silometopus reussi (Thorell) 259 Zelotes mundus (Kulczyński) 170 Pirata latitans (Blackwall) 152 Pocadicnemis juncea Locket & Millidge 129 3 Trochosa ruricola (de Geer) 74 54 Syedra apetlonensis Wunderlich 105 4 Species of conservation interest Crustulina sticta (O. P.-Cambridge) 1 1 Enoplognatha mordax (Thorell) 1 Silometopus bonessi Casemir 2 1 Tallusia vindobonensis (Kulczyński) 4 Trichopterna thorelli (Westring) 39 Arctosa figurata (Simon) 1 Lycosa singoriensis (Laxmann) 1 Pardosa cribrata Simon 52 Pardosa maisa Hippa & Mannila 26 Argenna patula (Simon) 1 13 Clubiona subtilis L. Koch 24 9 Haplodrassus minor (O. P.-Cambridge) 12 28 Micaria romana L. Koch 8 Zora armillata Simon 13 Thanatus arenarius Thorell 1 8 Thanatus striatus C. L. Koch 2 9 Sitticus inexpectus Logunov & Kronestedt 6 Table 1: Dominant and rare species in ungrazed (U) and grazed (G) meadows in the Seewinkel. A complete list is given in Zulka et al. (1997). Fig. 2: Species accumulation curve. Development of the spider species inventory in the Seewinkel region, plotted as cumulative number of recorded species against successive studies. Species assemblages As described, one of the major problems is the spread of reed vegetation, overgrowing salt pan shores and open grassland. Grazing management as a conservation tool (Rauer & Kohler, 1990) was accompanied by research on grazing effects. Among others, invertebrates of a grazed and an ungrazed meadow were recorded by pitfall trapping (performed from 9 April to 26 October 1990: Lethmayer, 1992). The ungrazed meadow contains a number of rare wetland species (Table 1, see also Zulka et al., 1997), e.g. Trichopterna thorelli (Westring), Clubiona subtilis L. Koch and Pardosa maisa Hippa & Mannila (see below). Syedra apetlonensis Wunderlich, a species recently described from the Seewinkel pastures (Wunderlich, 1992) and named after a village in the salt pan region (Fig. 1), also occurs abundantly in this habitat. In contrast, the grazed meadow can be regarded as a compound assemblage of disturbance tolerators (e.g. Pardosa agrestis (Westring)) and halophilic species (e.g.
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